If a researcher studies the effectiveness of anti-drug commercials by comparing the self-reported frequency of drug use among teens six months before and six months after the commercial aired, she is using an design.
a. cross-lagged panel
b. cross-sectional
c. ex post facto
d. pretest/posttest

If a researcher studies the effectiveness of anti-drug commercials by comparing the self-reported frequency of drug use among teens six months before and six months after the commercial aired, she is using an Pretest/posttest design.

Option D

Explanation:

The pre-test is defined as a test carried out on a product or  service before it is set to enter into the market for sale. It is  usually done to check not only the effectiveness and efficiency of the  product or service but also to check the safety of it too.

Sometimes  a product or service is exposed to text after it enters the market.  This is known as post-test as that is carried out after the product  enters the market.

c. taught scientists many new things about the earth, but not other planets.

explanation: